Sanches Júlia Olien, dos Santos-Pinto Lourdes Aparecida Martins, dos Santos-Pinto Ary, Grehs Betina, Jeremias Fabiano
Araraquara Dental School, São Paulo State University.
Dental Press J Orthod. 2013 Jan-Feb;18(1):128-33. doi: 10.1590/s2176-94512013000100024.
The purpose of this study was to compare dental size measurements, their reproducibility and the application of Tanaka and Johnston regression equation in predicting the size of canines and premolars on plaster and digital dental casts.
Thirty plaster casts were scanned and digitized. Mesiodistal measurements of the teeth were then performed with a digital caliper on the plaster and digital casts using O3d software system (Widialabs©).The sum of the sizes of the lower incisors was used to obtain predictive values of the sizes of the premolars and canines using the regression equation, and these values were compared with the actual sizes of the teeth. The data were statistically analyzed by applying to the results Pearson's correlation test, Dahlberg's formula, paired t-test and analysis of variance (p < 0.05).
Excellent intraexaminer agreement was observed in the measurements performed on both dental casts. No random error was present in the measurements obtained with the caliper and systematic error (bias) was more frequent in the digital casts. Space prediction obtained by applying the regression equation was greater than the sum of the canines and premolars on the plaster and digital casts.
Despite an adequate reproducibility of the measurements performed on both casts, most measurements on the digital casts were higher than those on the plaster casts. The predicted space was overestimated in both models and significantly higher in the digital casts.
本研究旨在比较牙齿大小测量值、其可重复性以及田中（Tanaka）和约翰斯顿（Johnston）回归方程在预测石膏模型和数字化牙模上犬齿和前磨牙大小方面的应用。
对30个石膏模型进行扫描并数字化。然后使用O3d软件系统（Widialabs©），在石膏模型和数字化模型上用数字卡尺对牙齿进行近远中测量。使用回归方程，以下切牙大小总和来获得前磨牙和犬齿大小的预测值，并将这些值与牙齿的实际大小进行比较。通过对结果应用皮尔逊相关检验、达尔伯格公式、配对t检验和方差分析（p < 0.05）对数据进行统计分析。
在对两种牙模进行的测量中均观察到了检查者内部的高度一致性。用卡尺获得的测量中不存在随机误差，而在数字化模型中系统误差（偏差）更常见。应用回归方程获得的间隙预测值大于石膏模型和数字化模型上犬齿和前磨牙的总和。
尽管对两种模型进行的测量具有足够的可重复性，但数字化模型上的大多数测量值高于石膏模型上的测量值。在两种模型中预测间隙均被高估，且在数字化模型中显著更高。
